The present invention relates to Lawsonia intracellularis vaccines and methods for protecting against and diagnosing L. intracellularis infection. The products and processes of the invention are attainable, in part, as the result of an improved method for cultivating large scale supplies of L. intracellularis, including both a novel isolate of L. intracellularis of European origin and a method of preparing a lyophilized product containing the attenuated European isolate as vaccine product.
L. intracellularis, the causative agent of porcine proliferative enteropathy (“PPE”), affects virtually all animals, including: rabbits, ferrets, hamsters, fox, horses, and other animals as diverse as ostriches and emus. L. intracellularis is a particularly great cause of losses in swine herds in Europe as well as in the United States.
A consistent feature of PPE is the occurrence of intracytoplasmic, non-membrane bound curved bacilli within enterocytes in affected portions of intestine. The bacteria associated with PPE have been referred to as “Campylobacter-like organisms.” S. McOrist et al., Vet. Pathol., Vol. 26, 260-264 (1989). Subsequently, the causative bacteria have been identified as a novel taxonomic genus and species, vernacularly referred to as Ileal symbiont (IS) intracellularis. C. Gebhart et al., Int'l. J. of Systemic Bacteriology, Vol. 43, No. 3, 533-538 (1993). More recently, these novel bacteria have been given the taxonomic name Lawsonia (L.) intracellularis. S. McOrist et al., Int'l. J. of Systemic Bacteriology, Vol. 45, No. 4, 820-825 (1995). These three names have been used interchangeably to refer to the same organism as further identified and described herein.
L. intracellularis is an obligate, intracellular bacterium which cannot be cultured by normal bacteriological methods on conventional cell-free media and has been thought to require attached epithelial cells for growth. S. McOrist et al., Infection and Immunity, Vol. 61, No. 19, 4286-4292 (1993) and G. Lawson et al., J. of Clinical Microbiology, Vol. 31, No. 5, 1136-1142 (1993) discuss cultivation of L. intracellularis using IEC-18 rat intestinal epithelial cell monolayers in conventional tissue culture flasks. In addition, H. Stills, Infection and Immunity, Vol. 59, No. 9, 3227-3236 (1991) discusses using Intestine 407 human embryonic intestinal cell monolayers and GPC-16 guinea pig colonic adenocarcinoma cell monolayers in conventional tissue culture flasks.
Recently, an L. intracellularis vaccine has been approved for use in the United States, which vaccine is based on L. intracellularis isolates described and claimed in U.S. Pat. Nos. 5,714,375 and 5,885,823, both of which patents are herein incorporated by reference in their entireties. The above-described vaccine is sold by Boehringer Ingelheim Vetmedica, Inc., 2621 North Belt Highway, St. Joseph, Mo. 64506-2002, under the trademark ENTERISOL® Ileitis.